Current in plane magnetoresistive sensor having a contiguous hard bias layer located at back edge of stripe height

ABSTRACT

A current in plane giant magnetoresistive (GMR) sensor having a hard bias layer that extends along the back edge (strip height) of the sensor rather than from the sides of the sensor. The hard bias layer preferably extends beyond the track width of the sensor. Electrically conductive leads, which may be a highly conductive material such as Cu, Rh or Au, or may be an electrically conductive magnetic material extend from the sides of the sensor stack. The bias layer is separated from the sensor stack and from the leads by thin layer of electrically conductive material, thereby preventing current shunting through the hard bias layer.

The present invention is related to U.S. Patent Application entitled AMETHOD FOR MANUFACTURING A CURRENT IN PLANE MAGNETORESISTIVE SENSORHAVING A CONTINGUOUS HARD BIAS LAYER LOCATED AT BACK EDGE OF STRIPEHEIGHT, having application Ser. No. ______, filed on ______ to commoninventors.

FIELD OF THE INVENTION

The present invention relates to magnetoresistive sensors and moreparticularly to a current in plane magnetoresistive sensor having anelectrically insulating hard magnetic bias layer formed at the back edgeof the sensor opposite the air bearing surface (ABS).

BACKGROUND OF THE INVENTION

The heart of a computer's long term memory is an assembly that isreferred to as a magnetic disk drive. The magnetic disk drive includes arotating magnetic disk, write and read heads that are suspended by asuspension arm adjacent to a surface of the rotating magnetic disk andan actuator that swings the suspension arm to place the read and writeheads over selected circular tracks on the rotating disk. The read andwrite heads are directly located on a slider that has an air bearingsurface (ABS). The suspension arm biases the slider into contact withthe surface of the disk when the disk is not rotating but, when the diskrotates, air is swirled by the rotating disk. When the slider rides onthe air bearing, the write and read heads are employed for writingmagnetic impressions to and reading magnetic impressions from therotating disk. The read and write heads are connected to processingcircuitry that operates according to a computer program to implement thewriting and reading functions.

The write head includes a coil layer embedded in first, second and thirdinsulation layers (insulation stack), the insulation stack beingsandwiched between first and second pole piece layers. A gap is formedbetween the first and second pole piece layers by a gap layer at an airbearing surface (ABS) of the write head and the pole piece layers areconnected at a back gap. Current conducted to the coil layer induces amagnetic flux in the pole pieces which causes a magnetic field to fringeout at a write gap at the ABS for the purpose of writing theaforementioned magnetic impressions in tracks on the moving media, suchas in circular tracks on the aforementioned rotating disk.

In recent read head designs a spin valve sensor, also referred to as agiant magnetoresistive (GMR) sensor, has been employed for sensingmagnetic fields from the rotating magnetic disk. The sensor includes anonmagnetic conductive layer, hereinafter referred to as a spacer layer,sandwiched between first and second ferromagnetic layers, hereinafterreferred to as a pinned layer and a free layer. First and second leadsare connected to the spin valve sensor for conducting a sense currenttherethrough. The magnetization of the pinned layer is pinnedperpendicular to the air bearing surface (ABS) and the magnetic momentof the free layer is located parallel to the ABS, but free to rotate inresponse to external magnetic fields. The magnetization of the pinnedlayer is typically pinned by exchange coupling with an antiferromagneticlayer.

The thickness of the spacer layer is chosen to be less than the meanfree path of conduction electrons through the sensor. With thisarrangement, a portion of the conduction electrons is scattered by theinterfaces of the spacer layer with each of the pinned and free layers.When the magnetizations of the pinned and free layers are parallel withrespect to one another, scattering is minimal and when themagnetizations of the pinned and free layer are antiparallel, scatteringis maximized. Changes in scattering alter the resistance of the spinvalve sensor in proportion to cos θ, where θ is the angle between themagnetizations of the pinned and free layers. In a read mode theresistance of the spin valve sensor changes proportionally to themagnitudes of the magnetic fields from the rotating disk. When a sensecurrent is conducted through the spin valve sensor, resistance changescause potential changes that are detected and processed as playbacksignals.

When a spin valve sensor employs a single pinned layer it is referred toas a simple spin valve. When a spin valve employs an antiparallel (AP)pinned layer it is referred to as an AP pinned spin valve. An AP spinvalve includes first and second magnetic layers separated by a thinnon-magnetic coupling layer such as Ru. The thickness of the spacerlayer is chosen so as to antiparallel couple the magnetizations of theferromagnetic layers of the pinned layer. A spin valve is also known asa top or bottom spin valve depending upon whether the pinning layer isat the top (formed after the free layer) or at the bottom (before thefree layer).

The spin valve sensor is located between first and second nonmagneticelectrically insulating read gap layers and the first and second readgap layers are located between ferromagnetic first and second shieldlayers. In a merged magnetic head a single ferromagnetic layer functionsas the second shield layer of the read head and as the first pole piecelayer of the write head. In a piggyback head the second shield layer andthe first pole piece layer are separate layers.

Magnetization of the pinned layer is usually fixed by exchange couplingone of the ferromagnetic layers (AP1) with a layer of antiferromagneticmaterial such as PtMn. While an antiferromagnetic (AFM) material such asPtMn does not in and of itself have a magnetization, when exchangecoupled with a magnetic material, it can strongly pin the magnetizationof the ferromagnetic layer.

The push for ever increased data rate and data capacity results in aneed for GMR sensors having ever increased performance. One measure ofsuch performance (dr/R) is the change in resistance in response to amagnetic field (dR) divided by the nominal resistance, or “sheetresistance” (R). Parasitic resistance, such as from poorly conducingleads, contributes to the sheet resistance, thereby lowering the dR/Rperformance.

Another factor affecting performance in is free layer sensitivity. Thefree layer should be able to respond as freely as possible to thepresence to a magnetic field, especially at the ABS of the sensor wherethe field is primarily detected. That is to say that the free layer'smagnetic moment must be easily rotated in response to a magnetic field.This free layer sensitivity has been limited, however, by the competingneed for free layer stability. The moment of the free layer must remainbiased, even in the event of a high temperature event such as a headdisk contact or an electrostatic discharge (ESD). As heads become eversmaller, the ability of traditional hard bias layer structures tomaintain stable free layer biasing decreases. This is due in part to thereduced junction area at the sides of the sensor at which the hard biaslayer provides it's biasing magnetic field.

Therefore, there is a strong felt need for a structure that can providefree layer biasing that is both stable in a very small sensor and alsoprovides optimal free layer sensitivity at the ABS of the sensor, wherethe magnetic field from the medium is primarily detected. There is alsoa strong felt need for a structure for that can reduce parasiticresistance from the electrical leads, thereby increasing dR/Rperformance.

SUMMARY OF THE INVENTION

The present invention provides a current in plane (CIP) magnetoresistivesensor for use in magnetic recording that has a hard bias layer disposedat the back edge (stripe height) of the sensor. The sensor includes asensor stack having sides that define a track width and has a back edgeopposite the air bearing surface (ABS). The sensor stack is sandwichedbetween first and second non-magnetic, electrically insulating gaplayers, and has leads extending from the sides of the sensor stack thatessentially fill the space between the first and second gap layers. Thehard bias layer is formed at the back edge of the sensor stack and isseparated from the sensor stack and from the leads by an electricallyinsulating layer.

The hard bias layer may have a width that is larger than the track widthof the sensor and may extend beyond the sides of the sensor stack. Theleads may be constructed of a very highly conductive material, such asCu, Rh, Au or some other material. Alternatively, the leads may beconstructed of a material that is both electrically conductive andmagnetic with a high permeability. In this way the leads can serve asside shields.

The sensor can be constructed by a method that reverses the K3 and K5processes to perform the K5 process before the K3 process. In otherwords, the sensor can be constructed by first performing a masking andion milling procedure to define the track width of the sensor, and thenperforming a second masking and ion milling process to define the backedge (stripe height) of the sensor. When defining the back edge of thesensor, the mask used to define the back edge can have an opening thatnot only extends along the back edge of the sensor but also extendsslightly beyond the sides of the sensor. A thin layer of insulatingmaterial such as conformally deposited alumina can then be deposited,followed by a hard magnetic material such as CoPtCr.

These and other features and advantages of the invention will beapparent upon reading of the following detailed description of preferredembodiments taken in conjunction with the Figures in which likereference numerals indicate like elements throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of thisinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings which are not to scale.

FIG. 1 is a schematic illustration of a disk drive system in which theinvention might be embodied;

FIG. 2 is an ABS view of a slider illustrating the location of amagnetic head thereon;

FIG. 3; is an ABS view, taken from circle 3 of FIG. 2 illustrating asensor according to an embodiment of the invention;

FIG. 4 is a side cross sectional view, taken from line 4-4 of FIG. 3;

FIG. 5 is a plan view of a sensor according to an embodiment of theinvention;

FIG. 6A is a plan view of a sensor according to an embodiment of theinvention in an intermediate stage of manufacture;

FIG. 6B is an ABS view taken from line 6B-6B of FIG. 6A;

FIG. 7A is a plan view of a sensor according to an embodiment of theinvention in an intermediate stage of manufacture;

FIG. 7B is an ABS view taken from line 7B-7B of FIG. 7A;

FIG. 7C is an ABS view similar to FIG. 7C showing a later, intermediatestage of manufacture;

FIG. 8 is a plan view of a sensor according to an embodiment of theinvention in an intermediate stage of manufacture;

FIG. 9A is a plan view of a sensor according to an embodiment of theinvention in an intermediate stage of manufacture; and

FIG. 9B is a side cross sectional view taken from line 9B-9B of FIG. 9A.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description is of the best embodiments presentlycontemplated for carrying out this invention. This description is madefor the purpose of illustrating the general principles of this inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to FIG. 1, there is shown a disk drive 100 embodying thisinvention. As shown in FIG. 1, at least one rotatable magnetic disk 112is supported on a spindle 114 and rotated by a disk drive motor 118. Themagnetic recording on each disk is in the form of annular patterns ofconcentric data tracks (not shown) on the magnetic disk 112.

At least one slider 113 is positioned near the magnetic disk 112, eachslider 113 supporting one or more magnetic head assemblies 121. As themagnetic disk rotates, slider 113 moves radially in and out over thedisk surface 122 so that the magnetic head assembly 121 may accessdifferent tracks of the magnetic disk where desired data are written.Each slider 113 is attached to an actuator arm 119 by way of asuspension 115. The suspension 115 provides a slight spring force whichbiases slider 113 against the disk surface 122. Each actuator arm 119 isattached to an actuator means 127. The actuator means 127 as shown inFIG. 1 may be a voice coil motor (VCM). The VCM comprises a coil movablewithin a fixed magnetic field, the direction and speed of the coilmovements being controlled by the motor current signals supplied bycontroller 129.

During operation of the disk storage system, the rotation of themagnetic disk 112 generates an air bearing between the slider 113 andthe disk surface 122 which exerts an upward force or lift on the slider.The air bearing thus counter-balances the slight spring force ofsuspension 115 and supports slider 113 off and slightly above the disksurface by a small, substantially constant spacing during normaloperation.

The various components of the disk storage system are controlled inoperation by control signals generated by control unit 129, such asaccess control signals and internal clock signals. Typically, thecontrol unit 129 comprises logic control circuits, storage means and amicroprocessor. The control unit 129 generates control signals tocontrol various system operations such as drive motor control signals online 123 and head position and seek control signals on line 128. Thecontrol signals on line 128 provide the desired current profiles tooptimally move and position slider 113 to the desired data track on disk112. Write and read signals are communicated to and from write and readheads 121 by way of recording channel 125.

With reference to FIG. 2, the orientation of the magnetic head 121 in aslider 113 can be seen in more detail. FIG. 2 is an ABS view of theslider 113, and as can be seen the magnetic head including an inductivewrite head and a read sensor, is located at a trailing edge of theslider. The above description of a typical magnetic disk storage system,and the accompanying illustration of FIG. 1 are for representationpurposes only. It should be apparent that disk storage systems maycontain a large number of disks and actuators, and each actuator maysupport a number of sliders.

With reference now to FIG. 3, a magnetoresistive sensor 300 according toan embodiment of the invention includes a magnetoresistive sensorelement or sensor stack 302, sandwiched between first and non-magnetic,electrically insulating gap layers 304, 306, which can be constructedof, for example alumina (Al₂O₃). First and second electricallyconductive lead layers 308, 310 extend laterally from the sides of thesensor stack 302 between the first and second gap layers 304, 306.

The sensor stack 302 includes a magnetic free layer 312, a pinned layerstructure 314 and a non-magnetic, electrically conductive spacer layer316, constructed of, for example Cu. The free layer can be constructedof several magnetic materials such as Co or CoFe, or of a combination oflayers of different magnetic materials.

The pinned layer structure 314 may be a simple pinned structure or anantiparallel pined (AP pinned) structure, and may be either self pinnedor AFM pinned. For purposes of clarity, the pinned layer structure 314,is described as an AP pinned layer structure having first and secondferromagnetic layers 318, 320, which are antiparallel coupled across anon-magnetic, electrically conductive AP coupling layer 322 such as Ru.The first and second magnetic layers 318, 320 can be constructed of, forexample CoFe, NiFe or some combination of these or other materials. Alayer of antiferromagnetic material (AFM layer) 324 is disposed beneaththe pinned layer structure 314, and can be for example PtMn, IrMn orsome other antiferromagnetic material. The AFM layer 324 is exchangecoupled with the first magnetic layer 318 and strongly pins the magneticmoments of the magnetic layers as indicated by symbols 319, 321.

The sensor stack 302 also may include a seed layer 326 formed at thebottom of the sensor stack 302, which can be used to initiate a desiredcrystalline growth in the layers of the sensor stack 302. A cappinglayer 328, such as for example Ta or some other suitable material may beprovide at the top of the sensor stack 302 to protect the layers of thesensor stack from damage during manufacturing processes such asannealing. The sensor stack 302 has first and second lateral sides 330,332 that define the track width (TW) of the sensor.

The leads 308, 310 are constructed of an electrically conductivematerial such as Cu, Au, Rh or some other suitable electricallyconductive material. As can be seen, the leads can extend from one gap306 to the other gap 304, which allows the leads 308, 310 to be muchthicker than prior art designs. This a great advantage over prior artdesigns wherein the majority of the space between the gap layers washard bias material and only a small portion of the area was leadmaterial. Hard bias materials have an electrical resistivity of about50-60 μOhmcm, whereas the much more conductive lead material has aresistivity of only about 5-6 μOhmcm. Therefore the ability to fillessentially the entire area between the gap layers 304, 306 with themuch more highly conductive lead material advantageously results in avery highly conductive lead, thereby reducing parasitic resistance.

In one embodiment of the invention, the leads 308, 310 can beconstructed of a soft (high permeability) magnetic material such as NiFeor CoFe so that they can serve as side shields as well as leads.Although such magnetic materials do not generally exhibit as high aconductivity as other non-magnetic lead materials such as thosementioned above, the ability to construct very thick leads, as discussedabove, allows the use of such magnetic materials while still maintaininghigh conductivity. The side shielding provided by such magnetic leads308, 310 provides improved signal resolution, preventing the reading ofsignals from adjacent tracks of data. Therefore, such side shieldingprovides a great advantage in the ability to read signals at very smalltrack widths and very tight track spacing. As mentioned above, such sideshielding would not be possible in a head having hard bias extendingfrom the sides of the sensor and having relatively thin leads formedover the hard bias material. The magnetized hard magnetic material ofsuch traditional hard bias layers would not function as a magneticshield, and the leads, being relatively thin, would not be able to beconstructed of a magnetic shielding material.

With reference now to FIG. 4, which illustrates a cross sectional viewof the sensor 300 viewed perpendicular to the ABS, the sensor stack 302has a front ABS edge 338 and a back edge 340 at the back of the stripeheight opposite the ABS edge 338. An insulation layer 342 covers theback edge 340 of the sensor stack 302, and may extend over the first gaplayer 306. This insulation layer 342, preferably Al₂O₃, can be depositedin a single conformal deposition after the back edge of the sensor stackhas been defined by an ion milling or other material removal processthat will be in greater detail herein below.

With continued reference to FIG. 4, a hard bias layer 344, which can beconstructed of CoPtCr or some other suitable high coercivity hardmagnetic material extends from the back of the sensor stack 302. Thehard bias layer 344 is separated from the sensor stack 302 by theinsulation layer 342 in order to prevent shunting of sense currentthrough the hard bias layer 344. The hard bias layer can extend asignificant distance backward, away from the ABS in the stripe heightdirection. A seed layer 346 may be provided at the bottom of the hardbias layer 344. The seed layer 346 is preferably an electricallyconductive material that can be sputter deposited, providing anelectrically conductive substrate on which to sputter deposit the hardbias layer 344. The seed layer 346 is also preferably a material thathas a desired crystalline structure in order to promote a desiredcrystalline structure in the hard bias layer 344. The crystallinestructure of the hard bias layer 344 greatly affects its magneticproperties and therefore affects its performance as a hard bias layer.

Because the hard bias layer 344 has a high coercivity, it has theproperty that its magnetic moment maintains its orientation once it hasbeen magnetized. Therefore, by applying a high magnetic field, themagnetic moment 350 of the hard bias layer 344 can be set as shown in adesired direction parallel with the ABS surface 338. Flux closurebetween the hard bias layer 344 and the free layer 312 at the sides ofthe sensor stack will cause the free layer 312 to have a magnetic moment352 that is biased in direction parallel with the ABS as desired andantiparallel with the moment 350 of the hard bias layer 344.

With reference now to FIG. 5A a top or plan view of the sensor 300 showsthe sensor stack 302 and the leads 308, 310 extending from the sides ofthe sensor stack 302. Also as can be seen, the hard bias layer 344, andinsulation layer 342 extend beyond the trackwidth defining sides 330,332 of the sensor stack. The bias layer 344 provides a magnetic biasfield 350 that biases the magnetic moment of the free layer (not shownin FIG. 5). Flux closure of the magnetic bias field 350 at the sides ofthe sensor stack at the back edge of the sensor stack provides thedesired magnetic biasing in a direction parallel with the ABS. Extendingthe bias layer 344 slightly beyond the sides 330, 332 of the sensorstack 302 ensures that flux closure will properly bias the free layerwith a magnetic bias field that is parallel with the ABS. If the hardbias layer were constructed to extend only to the sides 330, 332 of thesensor stack, or even worse, were to terminate short of the sides 330,332 (within the track width region), then the flux closure of the biasfield 350 would cause the bias field 350 to have a large component in anundesirable direction perpendicular to the ABS at the point where itreaches the sensor stack 302. Conversely, by extending the hard biaslayer 344 beyond the sides 330, 332 of the sensor, the flux closure ofthe bias field 350 with the sensor stack 302, causes the bias field 350to be essentially parallel with the ABS at the point where it reachesthe sensor stack 302 (and the free layer 312). Another advantage tohaving the bias layer 344 extend beyond the sides 330, 332 of the sensoris that this leaves room for photolithographic misalignment and othermanufacturing tolerances. If the alignment of the bias layer definingphoto step (described in greater detail below) is slightly misaligned,the bias layer will still extend across the entire back edge of thesensor stack 302.

Providing free layer biasing at the back edge of the sensor providesseveral advantages over the prior art hard biasing at the sides of thesensor. First, the bias layer 344 provides uniform biasing across thetrack width of the sensor, whereas prior art free layers were biasedmore strongly at the outer edges (at the edges of the track width) thanat the center of the sensor. Another advantage is that biasing the freelayer provides improved GMR response. A magnetic signal from a magneticmedium will be able to affect the magnetic moment of the free layer muchmore readily near the ABS surface 338 than at the back edge 340 of thesensor because the front edge 338 of the sensor is closer to the medium.Since the free layer 312 is biased at the back edge 340, the front edgewill be more responsive (ie. less magnetically stiff) than the backedge. Modeling has shown that this biasing arrangement providessignificant signal response improvement. Another important advantage ofplacing the hard bias layer 344 at the back edge 340 of the sensorrather than at the sides 330, 332 is that is allows for the leads 308,310 to be constructed as magnetic shields as described above. This is animportant advantage, because in order to meet the needs of future hightrack density magnetic recording systems such side shielding will becritical to avoiding adjacent track interference.

With reference now to FIGS. 6A through 9B, a method of constructing asensor according to an embodiment of the invention is described. Withparticular reference to FIGS. 6A and 6B full film sensor stack layers602 are deposited over a substrate 604, which can be the first gap layer306. The sensor layers 602 are shown as a single layer for purposes ofsimplicity, but would of course include the various layers making up thesensor stack 302 as shown in FIG. 3.

With reference to FIGS. 7A and 7B, a mask 702 is formed over the sensorlayers 602. The mask 702 can be of various forms and may includemultiple layers, such as a layer of photoresist patterned over anantireflective coating. With the mask 702 formed, an ion mill 704 isperformed to remove portions of the sensor material 602 that are notcovered by the mask 702, thereby defining the sides 330, 332 of thesensor stack 302 (FIG. 3). With reference to FIG. 7C, an electricallyconductive material 706 can then be deposited to form the leads 308,310. The masking and milling process described above (that which definesthe sides of the sensor stack) is often referred to in the industry as“K5”.

With reference now to FIG. 8, a second mask 802 is formed over thepreviously deposited layers. This mask (often referred to as the K3mask) defines the back edge or “stripe height of the sensor. The sidesof the portions of the sensor material 602 disposed beneath the mask 802are show in dashes lines in FIGS. 8 and 9, although they would actuallybe hidden from view by the presence of the mask 802. As can be seen, themask has an opening defines the back edge (stripe height) of the sensor,but the opening also extends beyond the sides of the remaining sensormaterial 602. An ion mill (not shown) is then performed to removematerial exposed by the opening in the mask 802.

With reference to FIGS. 9A and 9B, a thin layer of non-magnetic,electrically insulating material 902 is deposited. The insulationmaterial 902 is constructed of a material that can be conformallydeposited. Such a material can be for example, alumina (Al₂O₃), whichcan be deposited by atomic layer deposition. Other deposition methodsmay be used as well. After the insulation layer has been deposited, alayer of magnetically hard (high coercivity) material 904 is deposited.Such a material may be for example CoPtCr. A seed layer capable of beingsputter deposited may be initially deposited followed by deposition suchas by electroplating of the hard magnetic material. After depositing theinsulation material 902 and the hard magnetic material 904 aplanarization process such as chemical mechanical polishing (CMP) (notshown) can be performed to removed excess material 902, 904 over themask 802 and to remove the mask 802 itself.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Other embodiments falling within the scope of the inventionmay also become apparent to those skilled in the art. Thus, the breadthand scope of the invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1. A current in plane giant magnetoresistive (GMR) sensor for use inmagnetic data recording, the sensor comprising: first and secondnon-magnetic, electrically insulating gap layers; a sensor stacksandwiched between and contacting the first and second gap layers, thesensor stack including a magnetic free layer, a magnetic pinned layerstructure and a non-magnetic spacer layer sandwiched between the freelayer and pinned layer structure, the sensor stack having first andsecond laterally opposed sides that define a track width, the sensorstack also having an ABS surface and a back edge surface opposite theABS surface and extending between the first and second laterally opposedsides; first and second non-magnetic electrically conductive leadsextending laterally from the first and second sides of the sensor stack,each lead extending substantially from the first gap layer to the secondgap layer; and a hard magnetic bias layer extending along the length ofthe back edge of the sensor stack between the first and second gaplayers, the hard bias layer being separated from the sensor stack by alayer of electrically insulating material.
 2. A sensor as in claim 1wherein, the layer of electrically insulating material separating thehard bias layer from the sensor stack also separates the hard bias layerfrom the first and second leads.
 3. A sensor as in claim 1 wherein thehard bias layer has a lateral width that is greater than the trackwidth.4. A sensor as in claim 1 wherein the hard bias layer extends laterallybeyond the first and second laterally opposed sides of the sensor stack.5. A sensor as in claim 1 wherein the first and second leads areconstructed of a material having a high electrical conductivity thatextends essentially from the first electrically insulating gap layer tothe second electrically insulating gap layer.
 6. A sensor as in claim 1,wherein the first and second leads are constructed of a materialselected from the group consisting of Cu, Au and Rh, which extendsessentially from the first electrically insulating gap layer to thesecond electrically insulating gap layer.
 7. A sensor as in claim 1wherein the electrically insulating material separating the hard biaslayer from the sensor stack comprises alumina (Al₂O₃).
 8. A sensor as inclaim 1 wherein the electrically insulating material separating the hardbias layer from the sensor stack comprises alumina (Al₂O₃) that has beendeposited by atomic layer deposition.
 9. A sensor as in claim 1 whereinthe electrically insulating material separating the hard bias layer fromthe sensor stack comprises a conformally deposited material and alsoextends over a portion of the first gap layer.
 10. A sensor as in claim1 wherein the first and second leads are constructed of a highlyconductive material having a resistivity of 5-6 μOhmcm, the highlyconductive material extending essentially from the first gap layer tothe second gap layer.
 11. A sensor as in claim 1 wherein theelectrically conductive lead material is non-magnetic and has a highconductivity.
 12. A sensor as in claim 1 wherein the electricallyconductive lead material comprises a high permeability magneticmaterial.